The connection system (1) for connecting a fluid line (6) to a fluid reservoir (3) located within a device (2) by way of a cannula (5), comprises a cannula holder (4) holding the cannula (5) and a movable cannula cover (7) and locking means (11) for said cover (7), preventing the movement of the cannula cover (7) in a first state covering the cannula. The system further comprises a receiving element (10) for receiving the cannula holder (4), the receiving element being adapted for fixation to the device (2) or the receiving element forming part of the device (2), said receiving element comprising releasing means (16) adapted for interaction with the locking means (11). The releasing means (16) and the locking means (11) are arranged to release the cannula cover (7) by said releasing means interacting with the locking means, so that the cannula cover is movable by the inserting force to expose the cannula when the cannula holder (4) is inserted into the receiving element (10), so that the cannula cover (7) is in a second state exposing the cannula when the cannula holder (4) is inserted within the receiving element (10). Thus a connection system is provided for easy and secure connection and no danger of injury by the cannula or staining of the cannula.
